skip hlindex update if its columns aren't in the write_set

sql/index/hlindex.h

@@ -30,7 +30,8 @@ class hlindex : public Sql_alloc
 {
 public:
   TABLE *table;
-  hlindex(TABLE *t) : table(t) { }
+  bool update_needed; // index columns are in write_set, only used for UPDATE
+  hlindex(TABLE *t) : table(t), update_needed(false) { }
   virtual ~hlindex();
 
   virtual int read_first(TABLE *tbl, KEY *keyinfo, const uchar *value,

sql/key.cc

@@ -1,5 +1,5 @@
 /* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
-   Copyright (c) 2018, 2021, MariaDB
+   Copyright (c) 2018, 2026, MariaDB plc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -449,6 +449,8 @@ void key_unpack(String *to, TABLE *table, KEY *key)
 /*
   Check if key uses field that is marked in passed field bitmap.
 
+  This is used to detect if updating the row might change the key value.
+
   SYNOPSIS
     is_key_used()
       table   TABLE object with which keys and fields are associated.

sql/sql_base.cc

@@ -38,6 +38,7 @@
                                                 // mysql_derived_filling
 #include "sql_handler.h"                        // mysql_ha_flush
 #include "sql_test.h"
+#include "key.h"                                // is_key_used
 #include "sql_partition.h"                      // ALTER_PARTITION_PARAM_TYPE
 #include "log_event.h"                          // Query_log_event
 #include "sql_select.h"
@@ -10214,6 +10215,8 @@ int TABLE::open_hlindexes_for_write()
   for (uint i= s->keys; i < s->total_keys; i++)
     if (hlindex_open(i) || hlindex_lock(i))
       return 1;
+    else
+      hli->update_needed= is_key_used(this, i, write_set);
   return 0;
 }
 
@@ -10239,7 +10242,7 @@ int TABLE::hlindexes_on_insert()
 int TABLE::hlindexes_on_update()
 {
   DBUG_ASSERT(s->hlindexes() == (hli != NULL));
-  if (hli && hli->table->in_use)
+  if (hli && hli->update_needed)
   {
     int err;
     // mark deleted node invalid and insert node for new row